David Aguilar: First functional LEGO® prosthetic arm

He may not be an Avenger but inventor, record-breaker and advocate for inclusion and innovation David Aguilar (Andorra) created a series of high-tech arm prostheses called MK-I, 2, 3, 4 and 5 with… you’ve guessed it, LEGO® bricks.

Also going by the nickname "Hand Solo", David created the world’s first functional LEGO® prosthetic arm when he was only 18.

Now a bioengineering student and an advocate for acceptance, David aims to create a more kind and inclusive world one LEGO® brick at the time.

David was only 9 years of age when he created his first prosthesis using the popular construction bricks.
Due to Poland Syndrome, a congenital disease that can cause abnormalities and underdeveloped muscles in the subject's limbs in arms, chest, shoulders and hands, David was born without a fully developed right forearm.
Begin different from the other children wasn’t easy for him in the beginning and, looking back, he recalls a lot of insensitive comments.

However, David didn’t allow the cruel words that other kids threw at him to get under his skin and kill his dreams and imagination. 

Instead, he sought refuge in games and comics, in pop culture and in building new worlds. 

“I became obsessed with LEGO,” he says at Great Big Story.

So obsessed in fact that, after building infinite planes, cars and houses, he decided he would build himself a brand-new arm with a building material he had mastered through and through.

"LEGO was my first toy as a kid, it felt that you could build an infinite amount of things," he says. "Imagination was the only limit!"

His father has been a continuous influence for David, and supported his ambition while being his partner in crime and biggest inspiration.

The two have co-written a book, "Piece by Piece" (Pieza a Pieza), and David commented that his dad played a fundamental role in helping him feel like any other child.

He also helped David play with LEGO® bricks as a child and became his unwavering companion in Hand Solo’s journey through the world of building and creating.

David and his dad show their co-written book,

A Real-Life Tony Stark

His very first prosthesis started taking shape when David was just a child. He was going to use the pieces from a boat set to achieve the shape for his prosthetic, but the classic LEGO® bricks weren’t strong enough to sustain the weight of the structure.

Other nine years had to pass before he could try again.

That’s how David’s very first fully-functioning mechanical prosthesis came to life.

The red structure he build was named MK-I (Mark 1) in honour of Iron Man’s worldwide famous red suit. 

Its movement was entirely mechanical and fully functional, entirely made using bricks from a LEGO® Technic Rescue Helicopter set (#9396). 

It featured a moveable elbow joint and a grabber for grabbing and picking up objects, and performing daily tasks… like push-ups! The grabber was activated by bending the elbow.

"My first model isn't motorized, I control it with my muscles and it becomes a bit painful once you spend a long time with it. Good thing is, the MK-I is strong enough to support my weight when performing some push-ups!"

In January 2017, David (and his MK-1) broke the record for the first functional LEGO® prosthetic arm. 

But that was only the beginning...

"I wanted to see myself in the mirror like I see other guys, with two hands."

– David Aguilar

David Aguilar MK arms green background

Hold on... What is LEGO® Technic?

Think your regular Lego, but make it harder, stronger and more durable.
That car you built as a child with classic LEGO® bricks? Make it stronger and with more complicated engines and all the features of a real-life, mechanical car. 

Their range includes several hard-mode building sets with racing cars, app-controlled off-roaders and motorbikes catered to a more adult audience. Surely, a piece of LEGO® we don’t want to step on!

A motorized LEGO® prosthetic arm

After that first attempt, David worked hard to better his existing MK-1 model.

Most people couldn’t believe a prosthetic arm could be made of LEGO®, but David proved all of them wrong and keeps doing so.

 His most upgraded and latest MK-V LEGO® prosthetic arm is motorized, with five fingers that he controls through subtle movements of his residual arm.

This specific model is remarkably more comfortable than the previous versions and holds a Spike Prime Hub – a programmable control unit capable of receiving and sending orders from sensors to motors. 

Therefore, it’s much easier and less tiresome to use since it doesn’t rely on David’s muscles to work.

"It's the most comfortable prosthetic of my models and I don't need to use my muscles to lift something. The servo motors do it for me!"

The main challenge David faces when building prosthetic arms is balancing functionality and comfort.

"You can't wear something very uncomfortable, even if it's super functional, and vice-versa."

From Han Solo to Tony Stark, David took continuous inspiration from the pop culture around him. 

A love for comics and classics reached its peak when, during an event at NASA, he was defined as "the real-life Tony Stark" by Charlie Wen, co-founder of Marvel's Visual Development department alongside Ryan Meinerding.

Smiling as he shows his creation, David is ready to help those in need

First functional foot-controlled LEGO prosthetic arm

Just like Tony Stark, the bioengineering student is an Avenger on a mission: to make prosthetic limbs that are affordable and accessible.

That is the case of eight-year-old young Beknur Bektemissova (Kazakhstan), who was born with both arms underdeveloped. 

Having heard of David’s record and incredible work, Beknur's family commissioned him two LEGO® prosthetics for their son.

Together with his father, Ferran Aguilar, David used LEGO® pieces to build a prosthetic arm with a built-in electronic stylus and presented the "eMK-Beknur" to Beknur’s family. 

Beknur and his mother travelled 1,300 kilometres from France to Andorra to receive the prosthetic arms from David, and Beknur couldn’t wait to try his new arms.

"With Beknur's case, I felt an immense joy and happiness when I saw him moving the LEGO® prosthetic for the first time,” David said.

“He was smiling so hard it was contagious!
I feel like if I'm lucky enough to keep building these prosthetics, I can help more children and people around the world."

The prosthesis features a grappling pincer, which is controlled by a cord connected to one foot. 

The price to create this set from LEGO® bricks was only 15 Euros ($18), making it fully functional at an accessible cost.

This will allow eight-year-old Beknur to move as he pleases while avoiding the prohibitive paywall of a classic prosthetic limb – which, between purchase and maintenance costs, are unaffordable for the majority of the public.

The "eMK-Beknur" prosthetic arm broke two records in 2021:

  • First functional foot-controlledLEGO® prosthetic arm
  • First functionalLEGO® prosthetic arm with a stylus

Hand Solo's future

But snatching a Guinness World Records title (or three!) was only the beginning of David’s future, as his imagination knows no limits.

Next, he plans to improve his existing MK-VI. 

For the future, he aims to create a model where hand and elbow move independently while achieving movements for all the different fingers.

The genius Hand Solo would also like to create more video and music rebuilds on his YouTube channel and, possibly, try his hand at models with 3D printing. 

 “Honestly that would be a game changer for my prosthetics!" he says.

 David Aguilar winning LEGOmaster France

David aguilar riding a scooter

David won LEGO® Masters France in 2021, and keeps racking up accolades worldwide. 


He is also one of the faces of LEGO®'s global campaign #RebuildTheWorld. 


As one of the biggest advocates for thinking outside the box and building with imagination, LEGO aims to inspire children and adults to unleash their creativity through this campaign. 

The goal? To rebuild a world with endless possibilities. 

But Hand Solo’s main objective is to give back, and to help those in need.

After completing his studies in bioengineering at the International University of Catalonia, one day David hopes to offer his creativity and skills to those in need – those who feel different and discriminated. 

He also recorded a documentary entitled "Mr Hand Solo". 

“[With the documentary] I hope to reach all your hearts and break with the stigma of disability for the sake of total inclusion and acceptance of the simple fact of being different,” he writes on his website. 

"All your dreams can be fulfilled if you want them very strongly. You just have to fight for them."

– David Aguilar

We can't wait to see where Hand Solo's journey will take him, and what amazing prothesis he will master next. 

Find more about David's accolades, creations and records inside the new Guinness World Records 2023, available in store and online from September 2022.

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